Brake-related problems account for over half of all violations that can bring a highway transport vehicle into an out-of-service state during roadside inspections. Brake problems are also a common cause of transport vehicle accidents, and have been cited as a factor in nearly 30% of all truck related accidents by the Commercial Vehicle Safety Association. For vehicle owners or operators of these vehicles, brake problems can therefore lead to costly downtime and, in the event of an accident, possible liability and insurance expenses.
In many cases, status of brake systems is assessed during roadside service inspections. These brake system inspections involve the measurement of the travel distance of the brake push rod to an accuracy level on the order of a fraction of an inch. However, it is estimated that 9% of vehicles that pass this test still have other brake issues that are difficult or impossible to detect without otherwise removing the wheel and/or dismantling the brake system and that warrant an out-of-service violation.
In-cab vehicle monitoring systems for highway transport vehicles are known. For example, U.S. Pat. No. 5,959,365 to Mantini et al. discloses an early warning device for tire rims and hub assemblies, comprising one or more individual axle spindle sensors, a programmable microprocessor for receiving and processing the sensor signals to detect an alarm condition, and alarm means to alert the driver of a problem with one or more of the wheels. The sensors are positioned in proximity to the axles and are capable of measuring heat, noise, vibration and/or knocking, which can be indicators of imminent detachment of the tire rim or the wheel hub assembly from the vehicle.
U.S. Patent Application Publication No. 20020019688 to Mantini discloses a brake monitoring system for trucks, tractors, trailers or buses using air brakes. An apparatus to monitor the braking system and the brake S-cam positioning comprises a positioning transducer which can convert the rotational movement of the brake S-cam camshaft to an electrical signal. This signal is used as the input to a microprocessor system for further analysis and comparison in determining the condition of the S-cam operations. The transducer signal not only provides the S-cam position, but the speed of rotation both in braking and release of the brakes. After analyzing the signal from the transducer with a microprocessor system some of the failure of the braking system can be detected. By comparing the signal from different wheels, the system can detect delays of applying brakes or delays of releasing brakes which also could be a failure condition of the air brake system.
While vehicle brake monitoring systems and methods are known, it is an object of the present invention to provide a novel vehicle brake monitoring system and method that overcomes deficiencies in such known systems and methods. Such deficiencies include, for example, the inability to distinguish slack from brake wear.